This invention comprises a method of producing transfers, particularly but not exclusively water slide transfers and especially firable transfers for use on ceramics, and also a method of decorating articles with such transfers.
Water slide transfers as used in the decoration of ceramics, glass, coated metals and plastics material and the like, commonly comprise a design formed from an ink system printed on to a water slide base paper, with an overprint of a covercoat. The base paper is water permeable and provided with a water soluble release layer to permit the design to be freed therefrom. The covercoat holds the print together and also provides some strength to the decal for handling. Typically the covercoats are solvent based and are printed by the screen process. During drying of the covercoats a considerable amount of solvent will evaporate therefrom. In order to maintain acceptable working conditions and meet the relevant legislation, it is necessary for the solvents produced to be extracted. This can produce considerable problems for the transfer producers, and the situation is likely to become more difficult as legislation becomes tighter.
Digital printing using techniques such as electrophotographic, ink jet, thermal wax and dye sublimation, has enabled the economic production of one off or short run transfer prints. However for water slide transfers a covercoat is still required to hold the transfer together. With overprinting of the covercoat this can be prohibitive for one off and short runs, therefore restricting the exploitation of digital technology for water slide transfers. Moreover, the overprinting of covercoat can lead to solvent attack of the inks, therefore restricting the choice of inks.
According to a first aspect of the invention there is provided a method of producing a water slide transfer, the method comprising forming a design on a backing paper with a soluble release layer thereon, forming a covercoat on a release paper, causing combination by placing the two papers on top of each other with the covercoat adjacent the design, and applying heat and/or pressure thereto such that the covercoat locates onto the design and can be freed from the release paper.
According to a second aspect of the invention there is provided a method of producing a water slide transfer, the method comprising forming a covercoat on a release paper, forming a design on the covercoat, causing combination with a backing paper with a soluble release layer by placing the two papers on top of each other with the design adjacent the release layer, and applying heat and/or pressure thereto such that the design and covercoat locate on the backing paper and can be freed from the release paper.
According to a third aspect of the invention there is provided a method of producing a transfer, the method comprising forming a covercoat on a release paper and forming a design on the covercoat.
The combination is preferably achieved by passing the two papers under a roller, which roller is preferably heated. The two papers may be passed between two rollers, which are desirably heated nip rollers. The, one or both of the rollers may be heated to a temperature of between 80 and 200xc2x0 C., and desirably between 110xc2x0 and 160xc2x0.
The covercoat preferably has a composition which softens during said heating. The covercoat preferably comprises a thermoplastics material and desirably a methacrylate resin or a cellulose derivative. The covercoat is preferably between 15 and 30 xcexcm thick, and may be applied to the release paper by screen printing.
The release paper preferably comprises a release layer, which may comprise polyethylene, polypropylene, a fluorocarbon or a chromium complex, e.g. Quilon (registered trade markxe2x80x94DuPont).
The design is preferably digitally printed. The design preferably incorporates inorganic colour pigments, and these may be applied within the toner system of an electrophotographic printer. In the second or third embodiments the design may be printed upon the covercoat.
The covercoat may incorporate a flux, and the flux may comprise up to 80% by weight of the covercoat. The flux may be a ceramic flux which melts at a temperature between 500 and 900xc2x0 C. The covercoat may be formed as a continuous layer, or may be provided on discrete parts of the release paper.
The invention also provides a method of producing a firable transfer according to any of the preceding nine paragraphs.
The invention further provides a water slide transfer made by a method according to any of the preceding ten paragraphs.
The invention still further provides a covercoat on a release paper according to any of said preceding ten paragraphs.
The invention yet further provides a method of decorating an article, the method comprising producing a transfer according to any of said ten preceding paragraphs, and applying the transfer to the article. With the first two embodiments water is preferably applied to the transfer to free the backing paper therefrom.
In the case of a firable article, the article is preferably fired subsequent to application of the transfer thereon.